As is known in the art, systems which may be used to test specimen samples such as blood samples, for example, add a single reagent to the sample in a chamber. The reagent reacts with the sample and cause the sample to emit light or to form a detectable product which, on further treatment, will emit light. Depending upon the presence of the constituent(s) of the sample a corresponding spectral distribution of the emitted light is provided. Furthermore, depending upon the specimen sample and the reagent added thereto the resultant luminescence occurs in a predetermined spectral range. The light emissions may be fed through a spectral filter and subsequently coupled to a photomultiplier tube and detector. Thus, with knowledge of the type of specimen sample, the type of reagent and the resultant spectral representation it is possible to determine the presence of certain substances in the specimen sample. Separate tests may be run with different reagents in the separate chambers to test for other constituents in the specimen.